An inorganic photoreceptor and an organic photoreceptor have been conventionally known as an electrophotographic photoreceptor (which, hereinafter, may also be simply referred to as “photoreceptor”) used in an image forming apparatus of an electrophotographic system. The “electrophotographic system” used herein is generally the following image forming process. A photoconductive photoreceptor is first charged, for example, by corona discharge in a dark place, and then exposed to an image to selectively dissipate charges only on an exposed portion, thereby obtaining an electrostatic latent image. This latent image is developed with a toner containing a colorant such as a dye and a pigment and a resin material, so that the latent image is made visible to form an image.
The organic photoreceptor has advantages in terms of degree of freedom of a photosensitive wavelength region, film forming property, flexibility, transparency of a film, mass productivity, toxicity, and cost, as compared to the inorganic photoreceptor. For this reason, the organic photoreceptor is currently used as most photoreceptors.
For a photoreceptor repeatedly used in the image forming process of the electrophotographic system, it is necessary that electrostatic characteristics typified by sensitivity, receptor potential, potential retention, potential stability, residual potential, said spectral sensitivity characteristics are excellent.
In order to improve the cleaning property of the photoreceptor, a process of roughening the surface of such a photoreceptor has been known. For example, in Patent Literatures 1 and 2 the addition of organic fine particles or inorganic fillers to a surface layer of a photoreceptor is disclosed as the process of roughening the surface of the photoreceptor.
However, such a photoreceptor has the problem in that the film strength decreases and the potential increases. Further, when a photoreceptor having coarse and large particles present on the surface is cleaned using a blade as a cleaning unit, the frictional force between the photoreceptor and the blade or the torque increases. As a result, the stick-slip and the turning up (reversal) of the blade occur. In addition, there are problems such as the abrasion of the blade.